Ekim

Hi All,
I am looking at getting some pros and cons about upgrading my flywheel and R&P.
I have an S2 that I DD and Track. Please everyone, I am looking for constructive posts and personal experiences with Lightened Flys and 5.12 R&Ps. I have done a lot of research and now I am looking for knowledge that others may have to input.

Junirol

iTrader: (24)

I think as far as DD, 5.12 gears will kill your fuel efficiency. You will have to keep your rpm higher than normal for cruising speeds (5k rpm for 70mph I think someone can check that), but for track you will have less power lost when you shift gears. Also your top speed will be lower, not like people drive their cars at top speed, just saying. Having a lighten flywheel you will rev faster (less rotating mass), so rev faster + less power lost = win on track in my book, but overkill for DD. I'd love to get the 4.77 gears from an S2 just need to find a used one somewhere.

Arca_ex

iTrader: (10)

If you daily the car stick with the 4.77's.

I've always wanted to step up to 4.77's from the 1st Gen 4.44 ratio but since I still drive the car on the street I wouldn't even think about doing 5.12's.

Ekim

I won't to migrate my car to more of a track/weekend toy. The mpgs already r bad....does anyone know how bad it would be with 5.12??

Prophet

Drive around at higher RPMS for a few weeks. Should give you an idea how bad it can get. Just hold a gear lower than you normally would and see what happens. It's not exact, but may give you an idea if no one has tried it with the drive gear swap.

Ekim

Hmmmmm that's an interesting idea I guess...
My primary thought is to extract the max performace out of the S2 and still scream around town and open it all up at the track....doesn't that sound appealling??

olddragger

iTrader: (3)

more to it than that. You have a 4:7 now with different transmission ratios than the S1's.
Its a good all around set up. S2's do accelerate faster on track than a stock s1--i have seen it time after time. So my advice is to leave it alone.
If you do end up going to the 5:12 you will end up spending a lot more time in the upper rpms. This means heat. So your cooling system will need work. For that matter it probably already dones for tracking purposes.
Now an easy way of doing this is to buy a set of track wheels and tires. Make them much shorter and your overall gear ration will go down a good bit.
This would be the best way I can think of --get the lower gearing and reduce the rotating weight/mass

Ekim

"much shorter"?
I know heat would be a concern, running constantly at higher rpms. Reducing rotating mass or unsprung weight Im sure would help. I wonder how much more heat would be generated...

Does anyone have any personal experience with the 5:12? This post is very much an exploratory action. I have already decided on the lightened flywheel, but the 5:12 R&P is up in the air some where for me....

From the few posts i've gotten so far, people say stick with my 4:77 and forget the 5:12...

jrx13

If it is a track car, I'd go with the 5.12.

I run a 4.88 on my RX-7, that originally came with a 4.10. I would have gone with a 5.12 if it wasn't double the price and because I'm on a budget. If you can afford it do it, it was one of the best track mods on my car I've ever done.

Oh and if your rules allow, I'd run a diff cooler as well.

Ekim

Thanks for the info. I was wondering abt using a diff cooler.

When/if I go 5:12, I would for sure retire my S2 from DD and just use it for tracking and terrorizing the BayArea.

Chris_Bangle

iTrader: (2)

Greatest post ever (mind you I had a few of those as well).

What kind of feedback do you need aside from logical a priori stuff?

Ekim

I just thought that a flywheel and 5:12 combination would be a awesome duo for the S2 drivetrain or any track toy rotary. lightened flywheel is pretty common and kind of a "duh", but I cant find much Data on what the 5:12. What kind of rpm and mph difference is there...idk how to explain this well

Example:
Stock/4:77 = 3rd gear ~4k rpm = 40mph ( dont quote me, just an example)
5:12 = 3rd gear ~4k rpm = 50mph

Sorry I dont have the proper terminology...

jrx13

You need to use a gear calculator. I have one that I use for my RX-7. If your in the SF Bay Area, I assume you will run Thunderhill. I use the main straight as my guide for top speed. I just wind 4th gear out to about 8000+ rpm on my car, the RX-8 can go to at least 9000 so you won't run out of gear. I have to run the RX-8 numbers in the excel program but this is my RX-7 chart. I like this calculator as it shows the mph & gear shifts throughout the chart rather than just redlline.

What size tires are you planning to run? I will input them in and post up the results.








As for diff cooling, you can check this thread here:
http://www.rx7club.com/showthread.php?t=794139

I'm pretty sure the drain & fill plugs have the same thread pitch & diameter as the RX-7s too but don't quote me on it.

Ekim

^^ Your awesome! Yes I run thunderhill mostly.
I run 245/40/18s

And I will check out that thread thanks!

jrx13

I'll try to work on the charts......give me a day or two.

As for the flywheel, which one are you planning to install? The lightweight one or the aluminum one? I had this talk with kster a couple weeks ago and I told him I had installed a Mazdaspeed lightweight flywheel on a Series 1 and couldn't even tell the difference unlike all the RX-7 ones I have installed. I told him that the aluminum would probably make a small difference but since he still drives his car around on the street I didn't think it would be a good choice. But if your car is mostly track, and if you do install the aluminum one, I'm sure he'd like to hear your feedback on it.

Ekim

Great thanks!

I see a lot of people raving about the BHR fly,but I am not sure. The replaceable friction plates are the plus there and BHR is well known High Quality products.

TeamRX8

iTrader: (25)

BHR sells an ACT flywheel, there is no such thing as a BHR flywheel

short tires not only add effective gear ratio, they also lower the CG/ride height

sblethen

iTrader: (3)

And possibly rotational mass...

On my phone but wanted to subscribe.

Stephen

Ekim

[QUOTE=TeamRX8;4200598]BHR sells an ACT flywheel, there is no such thing as a BHR flywheel

short tires not only add effective gear ratio, they also lower the CG/ride height[/QUOTE

They also have their own
http://blackhaloracing.com/?page_id=60&category=13

Are you saying I should get lower profile tires?

Ekim

I'm already starting to reduce unsprung weight with light wheels and rotors and so on....if that's what you both are referring to.

TeamRX8

iTrader: (25)

for me definitely since mine are only 23.8" OD ...


I may have miscalled it an ACT model, but it is rebadged at best. It probably comes with a pouch of koolaid and mad max secret sauce though, maybe a dash of authentic jamaican voodoo juju even ...

Ekim

Okay I see...
Do you have any recommendations Team? If so, why would you chose them?

bse50

Bhr sells a spec flywheel that's machined to tighter than required standards. Charles R. Hill will enlight you if you have any questions.
I have it, it has around 35 track hours and is holding up just fine.

If you don't care about the mpg get the 5.125 final gear, you will love it with the s2 ratios.
Driving style and suspension setups greatly influence your sidewall choice, think about it

Ekim

Mpg and the 5:12 definitely arent even in the same thought processes lol
The flywheel your talking about, is that the "BHR Flywheel" they have listed on their site? Is it just a modified SPEC Fly? Now that you mention it, it looks very similar

bse50

I don't remember how the flywheel came to life, you may want to ask such question to the company. PM Charles R. Hill here or send him an email!
Before moving to the s2 tranny i had better mileage with a 4.777 rp than the stock 4.444 when i was still using my car on the road. That's because of heavy stop and go traffic and average speeds, somehow i benefited from having shorter gears